The present invention relates to personnel monitoring systems.
Electronic personnel monitoring systems have been utilized in the criminal justice field for maintaining control of persons subject to a term of house arrest. A person subject to house arrest is required to remain inside his home at all times or during specified hours. House arrest programs are considered useful alternatives to conventional incarceration for convicted criminals and for criminal defendants awaiting trial. Thus, a person sentenced to house arrest will not be subject to the influence of long term criminals in a prison environment. Moreover, the person sentenced to house arrest can maintain relationships with his family and community. The house arrest sentence may be arranged so that the subject person is permitted to leave the house during working hours, and hence may maintain his employment. Moreover, prison space is a scarce and expensive resource. House arrest sentencing conserves this resource.
To maintain effective control of persons subject to house arrest, the controlling authority must monitor their actual compliance with the house arrest program. Thus, the controlling authority must check to see if each monitored person is in his home. Although this theoretically could be done by having officers visit each home at frequent intervals, such an arrangement normally is impractical in that it would require a large number of officers to maintain effective, frequent surveillance of a large group of individual homes. Therefore, automatic systems have been developed for monitoring the presence of persons at their respective homes or other detention locations.
One system which has been widely adopted for this purpose is described in U. S. Pat. No. 4,747,120. As set forth in the '120 patent, telephone dialer means at a central location such as the office of the controlling authority automatically initiates telephone calls from the central location via the community telephone exchange to each home or other remote location where a person is to be monitored. Instruction signal means automatically provide an instruction signal perceptible to the monitored person at the remote location during each such telephone call. In response to this instruction signal, the monitored person performs a predetermined action resulting in transmission of return signals from the remote location to the central location via the telephone line. Test means are provided at the central location for automatically testing the return signals from each home or remote location to determine whether the predetermined action has been performed by the particular person who is supposed to be present at the remote location called. If the test means at the central location finds that the proper return signals have been returned when a particular person's home has been called, then the test means have automatically determined that the person is home. If not, an alarm is generated at the central location. Typically, the system includes an identifying object or tag such as a coded bracelet which is attached to each person to be monitored. The test means may include means for determining whether the identifying object associated with a person assigned to a particular remote location was employed to generate the return signals received from that location. If so, then the proper person is present.
Systems as described in the '120 patent provide effective monitoring of parolees and other persons subject to house arrest at reasonable cost and with excellent security. Other remote monitoring systems employ a small, low-powered radio transmitter secured to each monitored person and a combination radio receiver and telephone dialer at each remote monitoring location. The receiver normally detects radio frequency signals from the transmitter while the monitored individual is present. If the monitored individual leaves the vicinity of the transmitter, he takes the small transmitter out of range and hence the receiver no longer detects the transmitter signal. In response to such a loss of signal, the telephone dialer is activated to automatically place a call to the central office and transmit an alarm signal to the central office.
Both of these systems use the telephone network. One drawback which has limited application of these systems heretofore has been that some persons to be monitored do not have a telephone line available in their home. This problem in particularly severe in some rural areas, where many homes do not have telephone service. Even in highly developed, urban areas a significant portion of criminals are poor and do not have a home telephone. Accordingly, monitoring systems which require a telephone line to the home have not been useful in monitoring these individuals. Moreover, criminal justice authorities have been concerned that house arrest monitoring systems which require a telephone line will be viewed as discriminating against poor people. Thus, an impoverished person who does not have a telephone may be sent to a conventional jail because he cannot be placed on a house arrest monitoring program.
There have accordingly been needs for further improvement in personnel monitoring systems.